Conductor roll



March 19, 1968 J w, o' L 3,374,165

CONDUCTOR ROLL Filed Feb. 18, 1965 Es. am A United States Patent3,374,165 CGNDUCTOR ROLL John W. Ollrien, Villa Park, and Arthur R.Stahllicrg, Park Ridge, ilk, assignors to Electra-Coatings, Inc, acorporation of Delaware Filed Feb. 18, 1965, Ser. No. 433,68$ 14 Claims.(Cl. 204-479) This invention relates to conductor rolls for use inelectric coating operations and to the manufacture of such rolls. Moreparticularly, this invention relates to a conductor roll having aseamless roll surface which can be used as an electrode in electrolyticplating or cleaning of sheet steel or the like for forming such productsas tin or galvanized plate.

It is common practice to use a conductor roll as the electrode incontinuous electrolytic cleaning and plating processes for coating metalfrom a solution or molten metal bath onto low carbon steel sheet to formtin or galvanized plate. Usually, solution plating, for example iscarried out using high speed plating baths of the plating solution. Thestock or sheet material to be plated is passed through the bath and heldimmersed in the bath during its passage therethrough by the conductorroll. An anode is placed on the other side of the stock from theconductor roll and spaced close to the roll. A low voltage, e.g., -30volts, power source is connected between the anode and the conductorroll, which functions as the cathode, to establish a direct currentfield between the anode and cathode and through the solution and stocksheet. In solution plating procedures, the direct current field isusually in the range of 400 to 800 amps er square foot. Normally, whenthe solution is a tin plating solution, for example, the direct currentfield will be snfficient to establish a current density of abnut 400amps per square foot; and, when the solution is a zinc plating solution,500-600 amps per square foot are usually suilicient. Bath or solutiontemperatures normally range from 90 F. to 160 F.

The sheet or stock material is usually pulled through the cleaning andplating baths at a high rate of speed, and the line tension can be asmuch as 4,000 pounds or more. Such tension may be generated by anapplied weight at the drag bridle station which magnifies throughhydraulic reaction against the stock material passing through thecleaning and plating tanks. Such line tension creates stresses on theshaft on which the conductor roll is mounted since the tension isapplied against the roll face as the stock material is pulled throughthe bath.

Further, the constant exposure of the conductor roll to acids in theplating bath and severe friction and heat generated by the electricalcurrent and heat of the plating bath, in addition to tension, presentproblems with respect to conductor roll life and roll maintenance. The

conductor roll must have excellent thermal and electrical properties.Carbon rolls, which have a thick (e.g., 4 inches) layer composed ofcarbon and a resin binder applied to an inner shell or shaft and haveacceptable electrical properties, have been used as conductor rolls, butthey are costly and susceptible of excessive wear.

It has been common practice to incorporate the very highly conductivemetals, such as copper, in conductor roll designs. In another prior artstructure, roll trunnions are constructed of still-cast copper while theroll body is formed from rolled and welded copper plate or cold drawnseamless copper tubing. To protect the copper surface against corrosionand erosion, the roll surface can be metalized with stainless steelmetal spray. Such stainless metalizing has not been very successfulbecause the applied metals do not have the hardness, bondingcharacteristics and dense grain structure required to transmit 3,374,165Patented Mar. 19, 1968 current and resist wear and corosion; wear causedby the stock sheet passin over the conductor roll increases the porosityof the stainless steel surface layer, resulting in picking up andretention of acids which eventually erode the stainless steel coatingwith resulting roll failure. Also, where protective layers are depositedby spraying metal on a roll surface of copper, the copper is porous anddoes not have consistent hardness. This condition creates hot spotswhich eventually cause failures in the bond between the copper surfaceand protective layer, resulting in roll failure.

In one successful approach, a conductor roll has been constructed havinga body portion entirely of steel. The journals are sleeved withstill-cast copper, and the roll body is electroplated or sprayed withmetal to retain a substantial thickness, e.g., inch, of copper; and thecopper surface is then electroplated with chrome or nickel to preventcorrosion. Although such roll has been successful in operation, itsconstruction is very expensive and the roll still presents manymaintenance problems, such as loss of the protective coatings of chromeor nickel after such coatings have become scored or gelled through use.

It has also been attempted to apply a rolled and welded stainless steelshell over a roll face; but it has been found that the Weld, whenexposed to acid, would discolor and mark the stock sheet beingprocessed, causing undue rejections. Further, such rolled and weldedstructures have poor tolerances with respect to roundness and requirethe use of a very heavy layer in order to ma chine the rollsurface tothe specified. roundness and finish While retaining proper layerthickness.

It is a general object of this invention to provide a new and usefulconductor roll of the character described.

It is another object of this invention to provide such a conductor rollwhich has good electrical and thermal conductivity, good strength andwear characteristics, which is resistant to corrosion and is of soundmechanical design.

Still another object of this invention is to provide a conductor rollhaving good electrical conductivity to the surface of the roll eventhough the surface is formed of a heavy layer of corrosion and wearresistant material which would not in itself provide such goodconductivity.

Yet another object of this invention is to provide a conductor rollhaving a replaceable surface layer which is not susceptible ofdiscoloring or marking the stock sheet material being processed in anelectrolytic coating system, so that only the surface layer, and not theentire conductor roll, need be replaced after excessive damage to thesurface.

Another object of this invention is to provide such a conductor rollwhich can be reground a number of times for removing surfaceimperfections and which has increased surface life between each requiredregrinding operation.

It is also an object to provide a conductor roll according to any of theforegoing objects in which the surface portion is positively lockedagainst movement relative to the remainder of the roll. i

Other objects will be apparent from the following description and thedrawings in which:

FIGURE 1 is a perspective view of a form of conductor roll in accordancewith the present invention;

FIGURE 2 is an enlarged section along line 22 through the conductor rollof FIGURE 1; and

FIGURE 3 is a section along line 3-3 of FIGURE 2.

While this invention is susceptible of embodiment in many differentforms, there are shown in the drawings and will be described herein indetail specific forms of the invention with the understanding that thepresent disclosure is to be considered as an exemplification of theprinciples of the invention and is not intended to limit the inventionto the forms or embodiments illustrated.

Turning now to the drawings, there is illustrated a conductor roll whichincludes an inner shell 12 having a cylindrical outer surface andsupported at each end by a trunnion 14. A shaft 16 passes centrallythrough trunnions 14, coaxial therewith, and is keyed to each oftrunnions 14 by a suitable key as shown at 18. The inner shell 12 isstrengthened by suitable support plates 20 spaced from shaft 16 andsecured to the inner surface of shell 12 to give stiffness to shell 14without transmitting forces through the support plates.

An outer shell 22 is provided in the form of a machinedcentrifugally-cast tubular member surrounding and tightly contractedagainst the outer surface of inner shell 12 so that outer shell 22 issecurely held as an outer layer against inner shell 12. A pair ofcorrosion-resistant end caps 24, e.g., of neoprene (polychloroprene)rubber or the like, cover the portions of trunnions 14 and the otherwiseexposed ends of inner shell 12 which would otherwise come into contactwith corrosive acids in the plating bath during use of the conductorroll.

The conductor roll illustrated is water cooled during its use and istherefore provided with water passages in the form of bores 26 in shaft16 for flowing water through the hollow interior of inner shell 12.Plates 20 are provided with passages indicated at 28 permitting freeflow of water throughout the shell interior, and a corrosion resistantcoating 30 is applied to the inner surfaces of the inner shell 12 andtrunnions 14.

The illustrated conductor roll can be mounted by suitable bearings,e.g., as indicated at 32, supported in walls of a cleaning or platingtank in an electrolytic coating system, or in any other normal mannerfor mounting a conductor roll.

The inner shell 12 is formed of a highly electrically conductive metalsuch as an allow of aluminum and copper. The shell can be formed byshaping and welding a plate in tubular shape or can be cast or formed inany other manner. Preferably, the metal of the inner shell includesabout 13 to 88 weight percent copper and about 9 to 85 weight percentaluminum. Compositions of suitable alloys are as follows:

ALLOY NO. 1

Element: Weight percent Aluminum 9 to Iron, maximum 1.5 Copper 88 Others.60

ALLOY NO. 2

Element: Weight percent Aluminum 84 to 86 Iron, maximum 1.5 Copper 13Others .60

ALLOY NO. 3

Element: Weight percent Aluminum 17 to 18 Iron, maximum 1.5 Copper 80Others .60

Of the above, the alloys numbers 2 and 3 are preferred because of theirlesser expense. Where high current carrying capacity is required, alloyshaving higher copper contents, and even copper alone, would be used.

The outer shell 22, it will be noted, is a seamless shell and isadvantageously formed by centrifugally casting, a procedure well knownin the art. Briefly, during centrifugal casting, a permanent metal moldis spun in a horizontal position while molten metal to be used informing the shell 22 is poured into the mold. The mold is of the 4correct size to provide the desired diameter of the seamless shell 22.The metal solidifies in the mold in the form of the shell and the shellis removed from the mold. The shell is then rough machined and heattreated to the desired hardness, e.g., to Brinell, for maximum corrusionand abrasion resistance.

The shell 22 is then assembled over the inner shell 12. Accordingly, theshell 22 is bored concentric at a close tolerance, e.g., .015 inch,slightly smaller than the diameter of the outer surface of shell 12. Theshell 22 is then heated, e.g., to about 500% F, to expand the shell,e.g., about .025 to .030 inch, to an inner diameter, larger than theouter diameter of shell 12, whereupon the shell is slipped over theinner shell and permitted to cool, providing an interference lit to theinner shell, e.g., or" about .018 to .022 inch. The trunnions 14 andshaft 16 can then be placed in position with trunnions 14 being weldedto the inner surface of shell 12. During heating of the outer shell toexpand, care should be taken not to heat to a temperature sufficient todestroy its desirable hardness properties. However, should suchtemperature be exceeded, it is only necessary to reheat the shell to ahighly elevated temperature followed by a period of controlledtemperature reduction until the shell regains its properties.

The preferred metal for the outer shell 22 is one which possessesexcellent corrosion and Wear resistant properties and is stillsumciently conductive so that, when backed tightly by the more highlyconductive inner shell 12 over the entire interior surface of the outershell 22, suflicient passage of electrical current is permitted throughshell 22 to the outer surface to carry out a normal plating operationusing a low voltage power source at a high current density. Oneparticularly preferred stainless steel alloy having such properties hasthe following non-ferrous chemical analysis:

CHEMICAL ANALYSIS (ELECTROLOY #9205) Columbian addition 8 times thetarget for carbon hardness 130 to 140 Brinell.

The trunnions 14 are of a highly electrically conductive material, as ininner shell 12, such as any of the aluminum and copper alloys numbers 1through 3 listed above. Shaft 16 can be of hot-rolled carbon steel, heattreated to 90,000 pounds minimum yield, giving excellent strength to theshaft. It will be noted that the shaft 16 is in electrical contact byits force-fit with trunnions 14- over a very large surface area givingsufiicient electrical contact to carry a 10 to 30 volt, 10,000 to 25,000amp load, e.g., as may be needed when fused electroplating tin is usedin lieu of a solution bath.

The conductor roll can also be provided with means for preventingrelative movement of the outer and inner shells so that the outer andinner shells will rotate together with the conductor roll shaft. Suchmeans preferably are positive holding means such as pins, welds or thelike and also also preferably electrically conductive. Referring toFIGURES 2 and 3, a plurality of electrically conductive pins 41 areprovided in bores extending from the outer surface of outer shell 22into the inner shell 12 for securing the outer shell against movementrelative to the inner shell. To include such pins in the structure, theouter shell. 22 is assembled on inner shell 12 as described above. Thestructure is then drilled from the outer surface of outer shell 22 intothe drum or shell 12 and tapped to receive the threaded pins 41. In theform shown, three pins were used at each end of the conductor rollequally spaced around the conductor roll.

The present conductor roll structure is suitable as a replacement forcarbon rolls and can be manufactured at as little as one-quarter toone-third the cost of the cast carbon rolls now in use. The presentrolls are comparative.y long lived and have markedly better wearcharacteristics. Also, the present conductor roll structure does notrequire niclrel and/ or chromium coatings on the exterior surface, whichmay have to be intermittently stripped and replaced as the conductorroll becomes Wom. Rather, the outer shell is of a corrosion resistantand wear resistant material; it is only necessary to regrind the surfacewhen it becomes unduly worn, and it has been found that a /8 inch thickouter shell can be reground three or four times before the outer shellneeds replacing. Replacement can be effected by stripping the old outershell from the inner shell, heating a new outer shell to expand andpermitting the new outer shell to contact over the inner shell asdescribed above. In normal use, the inner shell should never needreplacement due to corrosion.

It has further been found that the present conductor roll has a rolllife as much as four times that of a copper roll. Thus, four times asmuch material can be processed before regriuding of the roll isrequired. The longer roll life results in less down time and lower rollinventories.

Also, the cost of manufacture of the present roll is less when comparedto the cost of manufacture of a rolled and welded sheet applied to aninner shell, especially due to savings in materials used in the outershell layer. In the rolled and welded sheet structure, it has been foundnecessary to use a one-inch plate to give a three-eighths inch layerafter finishing, involving a cost about three times that of the seamlesscentri-cast layer.

We claim:

1. A conductor roll for use as an electrode in a bath of an electrolyticcoating or cleaning system, which comprises a shaft, an inner, highlyelectrically conductive, tubular metal shell, a highly electricallyconductive metal trunnion means supporting said inner shell on saidshaft for rotation therewith, and a seamless, outer, centrifugally cast,electrically conductive tubular metal shell contraction fitted on saidinner shell in compression force-fit with and covering the outer surfaceof said inner shell providing electrical connection between the innerand outer shells, the metal of said outer shell being highly resistantto acid corrosion and having lower electrical conductivity than themetal of said inner shell.

2. The conductor roll of claim 1 wherein the metal of said outer shellcomprises chromium-nickel stainless steel.

3. The conductor roll of claim 1 wherein the metal of said inner shellcomprises aluminum and copper.

4. The conductor roll of claim 1 including positive securing meanssecuring said outer shell against rotation relative to said inner shell.

5. The conductor roll of claim 1 wherein the metal of said inner shellcomprises an alloy of 13 to 88 weight percent copper and 9 to 85 weightpercent aluminum and contains no more than 1.5 percent iron.

6. The conductor roll of claim 1 wherein said shaft is steel.

7. The conductor roll of claim 1 wherein the metal of said trunnionmeans comprises an alloy of aluminum and copper.

8. The conductor roll of claim 1 wherein the metal of said outer shellcomprises stainless steel having the fol lowing non-ferrous analysis:

Element: Percent by weight Carbon, maximum .03 Chromium 19.0-22.0

Columbian addition 8 times the target for carbon hardeners to Brinell.

9. The conductor roll of claim 8 wherein the metal of said inner shellcomprises:

Element: Parts by weight Aluminum 9 to 10 Copper 88 Iron, maximum 1.5

10. The conductor roll of claim 8 wherein the metal of said inner shellcomprises:

Element: Parts by weight Aluminum 84 to 86 Copper 13 Iron, maximum 1.5

11. A conductor roll for use as an electrode in a bath of anelectrolytic coating or cleaning system, which comprises a steel shaft,a first tubular metal shell formed of electrically conductive metal,electrically conductive metal trunnion means of the same metal as saidfirst shell secured to and supporting said first shell on said shaft forrotation therewith, a seamless second tubular metal shell centrifugallycast of electrically conductive metal and having a normal inner diametersmaller than the outer diameter of said first shell but sufficientlyclose to the outer diameter of said first shell for thermal expansion ofsaid posed closely covering the outer surface of said first Shell andsurrounding said first shell while said second shell is in an expandedheated state relative to said first shell and being contraction fittedby cooling from the expanded heated state against the outer surface ofsaid first shell in tight contact therewith maintaining completeelectrical contact between the first and second shells, the metal ofsaid second shell being highly corrosion resistant to the bath andhaving lower electrical conductivity than the metal of said first shell,and electrically insulating means covering the portion of said trunnionmeans and ends of said inner shell exposed to the plating bath.

12. The conductor roll of claim 11 wherein said insulating means is alayer of polychloroprene rubber.

13. A conductor roll which comprises an inner electrically conductivetubular metal shell, means supporting said inner shell for rotationabout its axis, an outer severable electrically conductive tubular metalshell in tight surface-to-su'rface fit on said inner shell for providingelectrical connection between the inner and outer shells, and meanssecuring said outer shell for rotation with said inner shell.

14. The conductor roll of claim 13 wherein said secur- 'lng means iselectrically conductive.

References Cited UNITED STATES PATENTS 1,403,257 1/1922 Lewis 29-4472,095,719 10/1937 Sinclair 29447 2,958,742 11/1960 Palmer 204-279 XR3,014,266 12/1961 Samuels 29-447 3,047,478 7/ 1962 Marsh et al 204107 XRHOWARD S. WILLIAMS, Primary Examiner.

D. D. JORDAN, Assistant Examiner.

UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTION Patent No.3,374,165 March 19, 1968 John W. O'Brien et al It is certified thaterror appears in the above identified patent and that said LettersPatent are hereby corrected as shown below:

Column 4, lines 47 and 48, cancel "Columbian addition 8 times the targetfor carbon hardeness 130 to 140 Brinell" and insert Columbium addition 8times the carbon precent for target hardness of 130 to 140 BrinellColumn 6, lines 8 and 9, "cancel "Columbian addition 8 times the targetfor carbon hardeners 130 to 140 Brinell" and insert Columbium addition 8times the carbon percent for target hardness of 130 to 140 Brinell line34, after "said", second occurrence, insert second shell to an innerdiameter greater than the outer diameter of said first shell, saidsecond shell being dis- Signed and sealed this 23rd day of December1969.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. Attesting OfficerCommissioner of Patents

1. A CONDUCTOR ROLL FOR USE AS AN ELECTRODE IN A BATH OF AN ELECTROLYTICCOATING OR CLEANING SYSTEM, WHICH COMPRISES A SHAFT, AN INNER, HIGHLYELECTRICALLY CONDUCTIVE, TUBULAR METAL SHELL, A HIGHLY ELECTRICALLYCONDUCTIVE METAL TRUNNION MEANS SUPPORTING SAID INNER SHELL ON SAIDSHAFT FOR ROTATION THEREWITH, AND A SEAMLESS, OUTER, CENTRIFUGALLY CAST,ELECTRICALLY CONDUCTIVE TUBULAR METAL SHELL CONTRACTION FITTED ON SAIDINNER SHELL IN COMPRESSION FORCE-FIT WITH AND COVERING THE OUTER SURFACEOF SAID INNER SHELL PROVIDING ELECTRICAL CONNECTION BETWEEN THE INNERAND OUTER SHELLS, THE METAL OF SAID OUTER SHELL BEING HIGHLY RESISTANTTO ACID CORROSION AND HAVING LOWER ELECTRICAL CONDUCTIVITY THAN THEMETAL OF SAID INNER SHELL.